4.2  TEXT QUESTIONS:

1: Which of the following can be beaten into thin sheets.
(a) Zinc                            (b) Phosphorus
(c) Sulphur                     (d) Oxygen
Ans :  (a)  Zinc

2: Which of the following statements is correct.
(a) All metals are ductile.                      (b) All non-metals are ductile.
(c) Generally, metals are ductile.        (d) Some non-metals are ductile.
Ans:  (c) Generally, metals are ductile. However, mercury metal which is liquid at room temperature – cannot be drawn into wires and is not ductile.

3:  Fill in the blanks:
(a) Phosphorus is a very _________ non-metal.

(b) Metals are ________ conductors of heat and _________.

(c) Iron is ________ reactive than copper.(d) Metals react with acids to produce _________ gas.
Ans :
(a) reactive.                                          (b) Good, electricity.

(c) more                                                (d) hydrogen.

4:  Mark ‘T’ if the statement is true and ‘F’ if it is false.

  1. Generally, non-metals react with acids.         [F]
  2. Sodium is a very reactive metal.                       [T]
  3. Copper displaces zinc from zinc sulphate      [F]
  4. Coal can be drawn into wires.                           [F]

5:

6: Give reasons for the following.
(a) Aluminium foils are used to wrap food items.
Ans: Aluminium foils are used to wrap food items because aluminium metal is malleable. Therefore, it can be beaten into thin foils.

(b) Immersion rods for heating liquids are made up of metallic substances.
Ans: Metals are good conductors of heat and electricity. Therefore, immersion rods for heating liquids are made of metallic substances.so it heats the water quickly.

(c) Copper cannot displace zinc from its salt solution.
Ans: A metal can displace a less reactive metal from its salt in an aqueous solution. But zinc is more reactive than copper. Therefore, copper cannot displace zinc from its salt solution.

(d) Sodium and potassium are stored in kerosene.
Ans: Sodium and potassium are stored in kerosene because they are highly reactive elements. They can easily catch fire even when in contact with air.

7: Can you store lemon pickle in an aluminium utensil. Explain.
Ans: As lemon pickle contains acid it cannot be stored in metallic vessels as acids readily react with metals.
Concept insight: acids react with metals and produce salt and hydrogen.

8:

9: (a) What happens when: Dilute sulphuric acid is poured on a copper plate.
Ans: Copper does not react with dilute sulphuric acid. However when concentrated sulphuric acid is poured on a copper plate, copper reacts with sulphuric acid to liberate hydrogen gas.

(b) Iron nails are placed in copper sulphate solution.Write word equations of the reactions involved.
Ans: The reactivity of iron is more than copper. So, iron will displace copper from copper sulphate solution. In this reaction, the blue colour of copper sulphate fades.

10: Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas.

(b) Write down word equations of all the reactions taking place in this process.
Ans:(a) Add some water in the test tube in which gas is collected. Now, cover the test tube. Shake it well. Test the solution with blue litmus and red litmus. Blue litmus turns red. Thus, the nature of gas is acidic.
(b) Charcoal when reacts with oxygen forms carbon dioxide gas.

11. One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold Jewellery to the goldsmith to polish. Next day when they brought the Jewellery back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight.
Ans: To polish a gold ornament, it is dipped in an acid (called Aqua Regia). The outer layer of gold dissolves in the acid and the inner shiny layer is visible. Because of loss of upper layer of jewellery, its weight is reduced.